1. Field of the Invention
The present invention relates to a numerical controller that controls a machine tool or a robot. Particularly, the present invention relates to a numerical controller with a protective circuit at the time of submersion.
2. Description of the Related Art
Generally, when a printed circuit board to which a voltage is applied is submerged, electrolytic corrosion may occur in wiring and electrical components of the printed circuit board. When the electrolytic corrosion advances by submersion for a long period of time, this leads to disconnection of the wiring, and there is a need for exchange of the printed circuit board for restoration. However, as long as the voltage is not applied even when the printed circuit board is submerged, it is possible to reduce the damage caused by the electrolytic corrosion. JP 2005-311637 A discloses a technique for cutting off the voltage supply when detecting the water wetting in a portable terminal.
Further, there are also cases where data of a memory is lost due to the submersion. When the data of the memory is lost, it is necessary to re-enter the program, parameters and the like for restoration, and it takes time to restore the data. To facilitate the restoration from the memory data loss, it is necessary to leave the backup data. JP 2008-158762 A discloses a technique for retracting the data of the memory to an external server via a LAN, when detecting the water wetting in the mobile terminal.
At the time of an occurrence of flood damage caused by flooding of the river, tidal waves or the like, in some cases, the numerical controller is submerged. Generally, even when the numerical controller is submerged, it is possible to restore the numerical controller by washing it with fresh water. However, electrolytic corrosion occurs in wiring portions of the component and the printed circuit board to which the voltage is applied at the time of submersion, and in particular, in some cases, when the submersion time is a long, the wiring portions of the printed circuit board lead to disconnection. In this case, for example, even when performing the washing, it is not possible to restore the wiring portions since it leads to disconnection, it is necessary to replace the numerical controller, and thus it takes time to restore the numerical controller.
Meanwhile, even when the numerical controller is restored, in some cases, the internal memory data of the numerical controller is lost. In this case, if backup of the memory data is regularly performed, it is possible to return the memory data to the state before submersion by restoring the backed-up memory data. However, when the latest memory data is not backed up, it is necessary to re-enter the program or parameters, and thus, it takes time to recover the memory date.
Techniques disclosed in JP 2005-311637 A and JP 2008-158762 A are all related to a mobile terminal. In contrast, since a machine tool in which a numerical controller is used is generally greater than a mobile terminal, a time to some extent is required until the entire machine tool is submerged even when flood damage occurs. In addition, since water such as working fluid generally falls on a machine tool or a numerical controller under the environment in which the machine tool is installed, shutting the system down each time makes the production efficiency fall. Unlike a mobile terminal disclosed in JP 2005-311637 A and JP 2008-158762 A, since the numerical controller is often not connected to an external server, the retreat of the memory data may also become difficult.
Although a main power source is turned on when the numerical controller is running, when the numerical controller is not running, the main power source is cut off and is usually turned off. Further, the submergence of the numerical controller at the time of occurrence of flood damage may occur regardless of whether the main power source is turned on or turned off. Here, although the power source is required to perform operations such as the water wetting detection, disconnection of the battery and retreat of the memory data, in a case where the submergence of the numerical controller occurs at the time of turning-off of the main power source, since the supply of the power source is not performed, a situation of failing to perform the operations such as the water wetting detection, the disconnection of the battery and the retreat of the memory data is considered.